Fluid pressure braking system



.1939. m. BOWEN Em 2.174.615

FLUID PRESSURE BRAKING SYSTEM Filed Dec. 28, 1935 2 Sheets-Sheet l INVENTORS. #525567 C. flan 0v a a I 77 ATTORNEYS.

lllhl I 1''. c. BOWEN ET AL FLUID PRESSURE BRAKING SYSTEM Oct. 3, 1939.

Filed Dec. 28, 1935 2 Sheets-Sheet 2 hiws INVENTORS. #52 5527 6? flan 5v a BYCZQAEA/Cf 7' Patented Oct. 3, 1939 FLUID PRESSURE BRAKING: SYSTEM? Herbert C. Bowen and Clarence V. Gardner, De-

troit, Mich, assiznors to Hydraulic Brake Company, Detroit, Mich, a corporation or California Application December 28, 1935, Serial No. 56,512

This invention relates to fluid pressure braking systems and more particularly to a duplex braking system.

Broadly the invention fcomprehends a duplex fluid pressure braking system for a motor vehicle, one for actuating the brakes associated with the front wheels of the vehicle and the other for actuating the brakes associated with the rear wheels of the .vehicle' An object of the invention is to provide a du-r plex fluid pressure braking system having a single operating means.

Another object of the invention is to provide a duplex fluid pressure braking system having means for eoualizing varying pressures which may be produced in the system.

A fin'ther object of the invention is to provide a fluid pressure braking system including a fluid pressure producing device constructed endoperative to actuate two separate systems to equalize pressures in the systems, and to maintain at least one oi the systems efieetive in the event of failure oi the other system due to leakage or breakage.

Qther objects of the invention will appear from the following description taken in connection oath the accompanying drawings which form a of this specification, and in which,

is a schematic View of a fluid pressure stem embodying the invention;

a, vertical sectionai mew off a duplex sysa Fig. a fragmentary View in section iii trating one of the pistons of the fluid pressure producing device at the end of its compression stroire;

Fig. is a longitudinal sectional view substan tially on line Q B, Fig. 2.

Referring to the drawings ior more specific details of the invention, it represents a reservoir having two compartments i2 and i i and a filling opening it which may be closed as by a plug it having openings 2% for venting the reservoir to 4 the atmosphere:

A cylinder 22 formed at the bottom of the reservoir has ports 2i and 26, providing communipartment H of the reservoir, and a discharge port 3t controlled as by a two-way valve 36.

A fluid pressure delivery pipe or conduit 38 connected to the valve has branches l0 and 42 connected respectively to fluid pressure-actu v ated motors 44 arranged for the actuation of friction elements of the brakes; and, correspondingly, a fluid pressure delivery pipe or conduit 48 connected to the valve 36 has branches 48 and 50 connected respectively to fluid pressure actuated motors 52 arranged for the actuation of the friction elements oi the brakes.

The :duid pressure actuated motors 44 and 52 are arranged in pairs, one pair for actuating the brakes associated with the front wheels of the vehicle and the other pair for actuating the brakes associated with the rear wheels of the veicicle.

The brakes may he of eonventionai type, ineluding a. teaching plate a rotatabie drum 55 associated therewith, corresponding interchangeable friction elements or shoes 53 pivoted on the hacking plate, and a motor corresponding to the motors 3 3 and 52 arranged on the backing plate between the shoes and operative to spread the shoes into engagement with the drum as against the resistance oia retractiie spring connecting the shoes.

A piston reciproceble in the cyiinder 22 is retained against disniscement by a washer it seated on an annular ouider in the open end or the cylinder sees in piece by a retaining seated in a cire from the evibody of the piston provide in eonjunctio ith the wall or the cylinder an annular chamber ccnnmmicating by oi the port 2 with the compartment it of the reservoir. The head or the piston has a forvierdiy extending concentric pin it and a pin rality of spaced ports i5 providing communica tions between the annuiar chamber iii and that portion of the cylinder forward or the head of the piston, and a collapsible leak-proof cup "i6 seated on the head of the piston and embracing the pin '12 controls the ports M.

A dependent piston 13, reciprocahie in the cylinder forward oi the discharge port 28, has a circumferential groove in which is fitted a leakproof washer providing against seepage of fluid past the piston. ihe head of this piston, opposed to the head of the piston G2, has a forwardly extending concentric pin 82 and a leakproof cup 84 seated on the head embraces the pinand a spring 86 interposed between the cup in returning the piston 62 to its retracted po- 86 and the cup I6 on the piston 12 serves to retain the cups against displacement and also to assist Jacent the slot receives the pin when the piston isat the end of its compression stroke.

The head of the piston 18 comprises two parts, a fixed head 86 and a shell 98 movable relative thereto. The fixed head has an annular shoulder I00 on which the shell seats when the piston is on its compression stroke, a groove I02 providing a lip I06, and a plurality of longitudinal slots I86 providing communications between the groove I02 and the annular chamber 88. The shell 98 has an annular lip I08 adapted to register with the lip I04 on the fixed head during the compression stroke of the piston so as to present an unbroken seat fora leak-proof cup IIO. This cup is slidabiy mounted on a concentric extension II2 on the piston, and the cup has a plurality of spaced apertures providing for the free passage of fluid between the annular chamber 88 and that portion of the cylinder forward of the piston during the retraction stroke of the piston and when the piston is in its retracted position. A spring seat I suitably secured to the free end oi the projection II2 retains the cup H8 against displacement, and a spring 6 interposed between the spring seat I I8 and the two-way valve 86 retains the valve against displacement and also serves to return thepiston I8 to its retracted position.

The piston 62 has a recess H8 in its back for the reception of one end of a thrust pin I20 on the other end of which is a coupling I22 connected as by a flexible boot I24 to the open end of the cylinder for the exclusion of dust and other foreign substances. A rod I26 connects the coupling to a foot pedal lever I28 pivoted on a suitable support I80, and a conventional retractile spring, not shown, connects the pedal to a fixed support, also not shown.

In normal operation, when the operator depresses the foot pedal lever I28 to apply the brakes, force is transmitted from this lever through the rod I26 and thrust pin I20 to'the piston 62, resulting in moving the piston on its compression stroke. During the initial movement of the piston on its compression stroke the collapsible leak-proof cup 16 on-thehead thereof closes the port 26 and pressure is'iinposed on the fluid in the cylinder 22 forward of the piston re- Y ton 62 imposes pressure on the piston 18 resulting in movement of this piston on its compression stroke. During the initial movement of the piston I8 on its compression stroke, the shell 98 seats on the shoulder I00 and closes the passages m and "is through the head of the piston; and as the piston advances on its compression stroke pressure is imposed on the fluid in the cylinder forward of the piston I8 resulting in discharge of fiuid therefrom past the two-way valve 86 and through the discharge port 84 and fluid pressure delivery pipe 46 into the fluid pressure actuated motors 62, causing actuation of the motors with the resultant spreading of the shoes 58, into engagement with the drums 66 against the resistance of the retractile springs 60.

Because of the shiftabiiity of the piston I8, due to variations of pressures which may be produced in the separate systems, and because of a differential in adjustment of the brakes associated with the front wheels of the vehicle and or retracted position under the influence of a retractile spring. As the foot pedal lever returns to its normal position, the rod I26 and the thrust pin I20 are retracted, resulting in release of the piston 62, whereupon the piston 62 moves to its retracted position under the influence of the spring 86 assisted by the return of the piston 18 to its retracted position under the influence of the spring II6,

As the piston 62 moves to its retracted position a partial vacuum is created in the cylinder 22 forward of the piston 62 resulting in drawing fluid from the compartment I2 of the reservoir through the port 24 into the annular chamber 10, thence through the ports I4 in the head of the piston past the collapsible leak-proof cup I6 into that portion of the cylinder forward of the piston 62. During this period fluid is returning to the cylinder from the motors 64 under the influence of the retractile springs connected between the friction elements of the brakes.

As the piston 18 returns to its retracted position the shell 88 engages the pin 82, and as the piston I8 recedes communication between the annular chamber 88 and that portion of the cylinder 22 forward of the piston 18 is established so that fluid may flow freely from the compartment ll of the reservoir into the cylinder, during which time fluid is returning to that portion of the cylinder forward of the piston I8 from the motors 52 under the influence of the retractile springs 60, and any fluid in excess of the quantity required to completely fill the .cylinder is returned to the reservoir.

Under abnormal operations oi the brakes, as

for example, should the brakes associated with the front wheels of the vehicle become inoperative due to leakage or breakage of the fluid pressure delivery pipe or conduit 46 and its branches or the motors- 62 connected to the branches, the piston 62 would, on a subsequent operation, travel substantially one-half of its stroke before displacing fluid from that portion of the cylinder forward of thepiston 62, through the port 28, past the two-way valve 30, and through fluid pressure delivery pipes 88 into the motors 44, to cause actuation of the motors with the resultant spreading'of the shoes into engagement with the drums against the resistance of the retractile springs 60. During this operation the pressure on the fluid in the cylinderforward of the piston 62 actuates the piston 18 to a positlon where the clip 94 engages the pin 92 to retain the piston 18 against movement. Upon subsequeiltloperations there would be no loss of pedal travel because the piston 18 would remain fixed or stationary and that portion of the cylinder 22 between the pistons 82 and 18 would becompletely filled with fluid from the reservoir upon .the first retraction strcike of the piston 62 after the rupture.

As another example, should the fluid pressure delivery pipe 35 and/or its branches, or the motors 44 connected to the branches, become fractured to such an extent as to render the brakes associated with the rear wheels of the vehicle inoperative, the piston 62 would, after moving substantially one-half of its stroke, advance the pin 12 on its head into engagement with the pin 82 on the piston l8, and further movement of the piston 62 would move the piston 18 on its compression stroke resulting in actuation of the brakes associated with the front wheels .of the vehicle in the mannerhereinbefore described.

Although this invention has been described in connection with certain specific embodiments, the principles involved are susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

Having thus described the various features of the invention, what we claim as new and desire to secure by Letters Patent is:

1. A fluid pressure producing device comprising a cylinder, 9. piston reciprocable therein,

means for operating said piston, a'floating piston reciprocable in the cylinder, said floating piston having a slot therein, a pin rigid withsaid cyl-.-.

inder andextending into said slot to limit movement of said piston in both directons, and means carried by said floating piston and engageable with said pin to lock said piston in one position.

2. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein, said piston having a slot, a pin rigid with said cylinder and extending into said slot to limit movement of said piston in both directions, and means carried by said piston for engaging said pin to lock said piston in one position.

3. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein, said piston comprising relatively movable parts, said partsin one position providing a passage through said piston and in another position closing said passage, and a pin carried by said cylinder for limiting separating movement of said parts.

4. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein, said piston having a slot therein and comprising relatively movable parts, said parts in one position providing a passage through said piston and in another position closing said passage, and a pin carried by said cylinder for limiting movement 01 said piston and relative movement between said parts.

HERBERT C. BOWEN. CLARENCE V. GARDNER. 

